This invention relates to a fan drive and water seal for use with an electric motor and more particularly to a fan drive and a water slinging seal for an electric motor mounted vertically in an application such as a dishwasher. While the invention is described in detail with respect to such application, those skilled in the art will recognize the wider application of the invention described hereinafter.
There are many applications commonly known involving the vertical installation of electric motors where the shaft of the motor is utilized in a liquid environment, as for example, in the case of a dishwasher application. In these applications, great care is taken to protect the motor from exposure to water and in particular, to water carrying detergent. In such applications where water carrying detergent has access to the motor either directly as a result of a major seal leak or as a result of casual leakage over a period of time around or through a seal, the destructive effects of the water and detergent on the motor assemblies can be and usually is catastrophic. The hot water combined with the detergent is actively destructive to the coatings used in the windings of the motor and in addition, of course, can wash away the lubricants used at various points in the motor.
In addition to protecting the motor underlying the liquid containing sump, such as that involved in a dishwasher application, there is the additional requirement of cooling the motor while maintaining the integrity of the liquid free environment immediately adjacent to the motor. In addition to the concern for liquid leakage which can be damaging to the motor and the hot air environment in which the motor is operating in a application such as a dishwasher, there is the additional concern for ridding the motor of heat generated within the motor structure itself. An example of a fan external to the motor housing, where the rotor assembly includes vanes to move air from within the rotor cavity of the stator assembly as shown in U.S. Pat. No. 4,689,507 issued to the assignee of the present application, and an additional example of a drain assembly external to the motor used in a dishwasher type application wherein an overlying slinger type seal is utilized on the motor shaft to prevent any liquid or misting from traveling down the shaft and into the motor beyond the drain assembly is shown in U.S. Pat. No. 4,698,511, also issued to the assignee of the present application. In addition to the complexities of the problems of providing both cooling and sealing for motors used in the difficult environment of dishwasher applications, the problems with manufacturability or producibility of the assemblies used to provide the desired operational results and the cost of achieving these results for particular solutions has been quite measurable. The quality of the solution involved in achieving both the desired cooling and the sealing to protect the motor have left much to be desired. Utilizing a fan as a means of cooling is typically difficult because of the limited space available in these types of applications. This is true whether the fan is external or internal to the motor. Earlier versions of fan mechanisms, such as that disclosed in U.S. Pat. No. 4,689,507, have required the use of additional parts or adhesives to secure the fan to a motor shaft. In addition, seals of various types, including those combined with water slingers employed upon the shaft of the motor in an area where the water has access, if not for the slinger seal, have not provided the degree of sealing necessary to assure continuous seal integrity. Because seal integrity is an issue of immediate and paramount concern, both the design of the seal itself and the selection of the material to be used for the seal are critical. The design of the seal and the selection of the appropriate material must yield a result that provides and assures seal integrity over an extended period of time. Specifically a period of time commensurate with the desired life expectancy of the dishwashing machine, as a whole, is the objective where a seal is frequently subjected to the temperature extremes and chemical effects of detergent liquids during the normal course of use.